The need to supply the clinical environment with automated instrumentation has forced the development of a wide variety of instruments capable of performing various types of blood cell counts. Automated counting of red blood cells or erythrocytes, platelets, or leukocytes white blood cells may be accomplished by a variety of techniques. One class of instruments includes, for instance, those based on flow cytometry principles and may generally be described as operating by analyzing light scatter characteristics of cells which are individually passed in a single stream analysis through an area illuminated by a focused light source. Typically lasers are employed to provide the illumination required and the scatter measurements are taken in a plurality of angles.
Often, it becomes necessary to remove the scatter effects produced by one class of cells in order to preserve the accuracy of counts with respect to another class. This may be accomplished by employing a lysing reagent specific for the class of interest.
Presently, the assignee hereof commercially offers the ELT series of instruments which are capable of providing red blood cell, white blood cell and platelet counts as well as the five traditional parameters: HGB, HCT, MCV, MCH and MCHC. Recently however, the assignee has experienced an increasing demand by clinicians for white blood cell differential counts, i.e., the so-called 3-Part Dif counts. This requires additional instrument capability so that the three leukocyte subpopulations (lymphocytes, granulocytes and monocytes) can be enumerated. In order to accomplish this, it becomes necessary to selectively lyse the red blood cells without significantly and deleteriously affecting the scatter characteristics of white blood cells.
It is an object of the present invention to provide reagents which are capable of lysing the red blood cells without disadvantageously affecting the white blood cells while their light scatter measurements are being detected.
It is a further object that the lysing reagent operate with sufficient speed so that the throughput of the interrogating instruments are not deleteriously effected thereby.
It is another object of the present invention to provide a red blood cell lysing reagent having a leukoprotective action for use in an upgraded ELT series instrument whereby 3-Part Dif counts may be obtained.